Online ISSN
1751-8695
Print ISSN
1751-8687
IET Generation, Transmission & Distribution
Volume 1, Issue 3, May 2007
Volumes & issues:
Volume 1, Issue 3
May 2007
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- Author(s): F. Katiraei ; M.R. Iravani ; P.W. Lehn
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 369 –378
- DOI: 10.1049/iet-gtd:20045207
- Type: Article
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p.
369
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(10)
A systematic approach to small-signal modelling of a micro-grid system that includes conventional (rotating machine) and electronically interfaced distributed resource (DR) units is presented here. The proposed approach incorporates fundamental frequency deviations in the overall system model and provides a methodology for the analysis of autonomous micro-grid, which inherently is more prone to frequency changes than the conventional utility grid. The model represents (i) electro-mechanical dynamics of the synchronous machine including the exciter and the governor systems, (ii) dynamics of the voltage-sourced converter and its real/reactive power controllers and (iii) the network dynamics. The model is intended for the controller design/optimisation, evaluation of angle/voltage stability, investigation of torsional dynamics, controller interactions of electronically interfaced DR units and low-frequency power quality issues. Typical results from application of the proposed modelling approach to a study system are presented. The results are qualitatively verified on the basis of the comparison with those obtained from time-domain simulation in the PSCAD/EMTDC environment. - Author(s): L.T.M. Mota ; A.A. Mota ; A. Morelato
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 379 –387
- DOI: 10.1049/iet-gtd:20050358
- Type: Article
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p.
379
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This paper proposes a method to forecast load behaviour during restoration of power systems after total or partial blackouts. Load behaviour after blackouts can be anomalous and differ significantly from that during normal operation conditions. A heuristic top-down approach was adopted to develop the forecasting method, using an expert system based on linguistic variables and fuzzy logic rules as its central core. The approach addresses the main aspects of load behaviour during re-energisation and is capable of representing physical phenomena. The proposed methodology was tested with data from real electrical power substations and these test results are presented. - Author(s): Y.F. Liu and F.F. Wu
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 388 –398
- DOI: 10.1049/iet-gtd:20060172
- Type: Article
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p.
388
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(11)
Here, the risk-constrained generation decision in a dynamic oligopolistic electricity market using stochastic optimal control is studied. In this formulation, the generation competition process is modelled as a dynamic feedback system, taking into account the system demand variation and generators' adaptive behaviours. Using the proposed framework, the risk-constrained strategic bidding is investigated with stochastic optimal control. Two common methods of risk management are discussed: the min–max regret technique and the mean–variance technique. It is found that the risk-constrained decision always results in less generation. - Author(s): Y.H. Liu ; L.B. Perera ; J. Arrillaga ; N.R. Watson
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 399 –404
- DOI: 10.1049/iet-gtd:20060240
- Type: Article
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p.
399
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(6)
The self-commutating multilevel current reinjection (MLCR) reduces the converter current waveform to zero during the valves commutations and, thus, removes the converter dependence on line commutation. This property provides the conventional thyristor converter with the same flexibility as the self-commutating multi-level schemes in terms of reactive power control and harmonic elimination. This paper describes the structure and control of a current source HVDC transmission scheme using MLCR converters. Extensive EMTDC simulation is carried out to demonstrate the improved controllability of the proposed HVDC configuration. - Author(s): S.K. Srivastava and K.L. Butler-Purry
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 405 –413
- DOI: 10.1049/iet-gtd:20060168
- Type: Article
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p.
405
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(9)
The electric power systems in US Navy ships supply energy to sophisticated systems for weapons, communications, navigation and operation. During battle, various weapons may attack a ship causing severe damage to the electrical system on the ship. This damage can lead to de-energisation of critical loads which can eventually decrease a ship's survivability. It is very important therefore to maintain the availability of power to the loads that keep the power system operational. There exists technology for ships that can detect incoming weapons. This knowledge can be used to determine reconfiguration actions which can be taken before the actual hit to reduce the damage to the electrical system when the weapon hits. Then reconfiguration for restoration can be performed after the hit to reconfigure loads de-energised by the damage from the hit. A new automated probabilistic predictive self-healing methodology to determine such reconfiguration control actions is presented. Implementation of these actions will lead to less damage caused by a weapon hit and can considerably improve a ship's chances of surviving an attack. This probabilistic approach entails three major functions: weapon damage assessment, pre-hit reconfiguration before a weapon hit for damage reduction and reconfiguration for restoration after a weapon hit to restore de-energised loads. A case study is presented to illustrate the new methodology. - Author(s): W. Uturbey and A. Simões Costa
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 414 –421
- DOI: 10.1049/iet-gtd:20060028
- Type: Article
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p.
414
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This paper deals with the representation of price-responsive loads in the short term coordination of predominantly hydroelectric hydrothermal systems. The proposed approach allows the representation of cross-relationships between demand and price during different dispatch intervals of a given time horizon. Also, consumer energy constraints which behave as dynamic restrictions can be taken into account. By that means, a load shifting program in which the consumers' overall energy consumption remains constant throughout the time horizon can be simulated. The short-term hydrothermal coordination is solved as a single optimisation problem employing the primal–dual interior point method. Realistic subsystems, based on the Brazil interconnected power system, are used to illustrate the effect of price-responsive loads on reservoir storages. - Author(s): Y. Li ; H.-D. Chiang ; B.-K. Choi ; Y.-T. Chen ; D.-H. Huang ; M.G. Lauby
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 422 –431
- DOI: 10.1049/iet-gtd:20060044
- Type: Article
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p.
422
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(10)
Load representation has a significant impact on power system analysis and control results. Currently, static load models are still popular in power industry for transient stability analysis. Dynamic load models are recommended in both industry and academia for possible improvement in analysis accuracy. The accuracy of using static (nonlinear) load models with suitably identified parameters for transient stability analysis is examined. Numerical studies conducted using on-line measurement data indicate that static load models, as compared with induction motor load models, are acceptable for modelling real power behaviours during disturbances and hence are adequate for transient stability analysis. Using multiple sets of on-line measurements, representative model parameters of five static nonlinear load models are derived and their performance in modelling dynamic behaviours of both real and reactive powers is compared. A method is presented to determine a representative set of parameters of static (nonlinear) load models for each loading condition. - Author(s): M. Prodanović ; K. De Brabandere ; J. Van den Keybus ; T. Green ; J. Driesen
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 432 –438
- DOI: 10.1049/iet-gtd:20060064
- Type: Article
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p.
432
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The introduction of distributed generation, DG, into low-voltage (LV) networks opens up the possibility of supplying ancillary services to aid network management and to maintain power quality. DG itself can cause voltage magnitude difficulties when injecting real power into networks with high R/X ratios, but control of reactive power injection can help overcome this. Continuous control and support only at the voltage limit conditions (to avoid unnecessary reactive power flows in normal conditions) are explored. Relatively high-impedance LV networks are prone to harmonic distortion from nonlinear loads. A variety of control methods that emphasise either harmonic-line flows or local-voltage distortion are examined, and a compromise method based on resistance emulation is shown to be effective. Experimental results from a single-phase laboratory network and 2 kVA inverter are used to illustrate how these additional control functions can be integrated into the existing control scheme for real-power management. Decomposition of observed voltages and currents into harmonic terms that are phasesynchronised to the grid voltage is a challenge in real-time systems. Kalman observers are used to achieve this with an additional advantage of avoiding explicit phase-locking while producing quadrature components useful in instantaneous calculation of reactive power and in providing feed-forward compensation terms. - Author(s): A.M. Leite da Silva and G.P. Alvarez
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 439 –446
- DOI: 10.1049/iet-gtd:20060191
- Type: Article
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p.
439
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A new probabilistic methodology to evaluate the operating reserve requirements of power systems in deregulated energy markets is presented. The main objectives are the assessment of reserve requirements for all submarkets (i.e. regulation, spinning, non-spinning and replacement), and the determination of the maximum acceptable bid prices in these submarkets and eliminating possible speculations. In order to balance reliability and costs, the proposed methodology is based on merging the loss of load cost index into the capacity bidding process for all operating reserve submarkets, thus avoiding the a priori establishment of an arbitrary risk index as a reference criterion. The results of studies using different test systems, including the IEEE-reliability test system and a configuration of the Brazilian South–Southeastern system, are presented and discussed. - Author(s): C.-L. Chen
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 447 –455
- DOI: 10.1049/iet-gtd:20060208
- Type: Article
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p.
447
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The rise of environmental protection and the progressive exhaustion of traditional fossil energy sources have increased the interests in integrating wind energy sources into existing power systems. Development of better wind-thermal coordination algorithms is necessary to determine the optimal proportion of wind generator capacity that can be integrated into the system for operating an isolated hybrid power system reliably and efficiently. A stochastic searching technique, which utilises a simulated annealing (SA) approach combined with an efficient constrained dynamic economic dispatch (CDED) method, is developed to coordinate the wind and thermal generation scheduling in isolated power systems with large integration of wind capacity. The SA algorithm is used for the scheduling of the generating units, whereas a direct search method routine carries out the ramp rate CDED when considering wind power generation. Several technique constraints are applied to determine the maximum proportion of wind generator capacity that can be integrated into the system. A constraint satisfaction technique for generating feasible neighbouring solution is also developed to improve the SA solution process. Numerical experiments are included to understand the wind generator capacity in the operating cost analysis and to provide valuable information for both the operational and planning problems. - Author(s): A.Y. Saber ; T. Senjyu ; A. Yona ; T. Funabashi
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 456 –465
- DOI: 10.1049/iet-gtd:20060252
- Type: Article
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p.
456
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A fuzzy adaptive particle swarm optimisation (FAPSO) for unit commitment (UC) problem has been proposed. FAPSO reliably and accurately tracks a continuously changing solution. By analyzing the social model of standard PSO for the UC problem of variable resource size and changing load demand, the fuzzy adaptive criterion is applied for the PSO inertia weight based on the diversity of fitness. In this method, the inertia weight is dynamically adjusted using fuzzy IF/THEN rules to increase the balance between global and local searching abilities. Velocity is digitised (0/1) by a logistic function for the binary UC schedule. To improve knowledge, the global best location is also moved instead of a fixed one in each generation. To avoid the system to be frozen, stagnated/idle particles are reset from time to time. Finally, benchmark data and methods are used to show effectiveness of the proposed method. - Author(s): X. Gu and C.A. Cañizares
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 466 –475
- DOI: 10.1049/iet-gtd:20060265
- Type: Article
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p.
466
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Determining loadability margins to various security limits is of great importance for the secure operation of a power system, especially in the current deregulated environment. Here, a novel approach is proposed for fast prediction of loadability margins of power systems based on neural networks. Static security boundaries, comprised of static voltage stability limits, oscillatory stability limits and other operating limits such as generator power output limits, are constructed by means of loading the power system until these security limits are reached from a base operating point along various loading directions. Back-propagation neural networks for different contingencies are trained to approximate the security boundaries. A search algorithm is then employed to predict the loadability margins from any stable operating points along arbitrary loading directions through an iterative technique based on the trained neural networks. The simulation results for the IEEE two-area benchmark system and the IEEE 50-machine test system demonstrate the effectiveness of the proposed method for on-line prediction of loadability margins. - Author(s): N. Mo ; Z.Y. Zou ; K.W. Chan ; T.Y.G. Pong
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 476 –483
- DOI: 10.1049/iet-gtd:20060273
- Type: Article
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p.
476
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A novel approach based on the particle swarm optimisation (PSO) technique is proposed for the transient-stability constrained optimal power flow (TSCOPF) problem. Optimal power flow (OPF) with transient-stability constraints considered is formulated as an extended OPF with additional rotor angle inequality constraints. For this nonlinear optimisation problem, the objective function is defined as minimising the total fuel cost of the system. The proposed PSO-based approach is demonstrated and compared with conventional OPF as well as a genetic algorithm based counterpart on the IEEE 30-bus system. Furthermore, the effectiveness of the PSO-based TSCOPF in handling multiple contingencies is illustrated using the New England 39-bus system. Test results show that the proposed approach is capable of obtaining higher quality solutions efficiently in the TSCOPF problem. - Author(s): J.C.M. Vieira ; W. Freitas ; D. Salles
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 484 –491
- DOI: 10.1049/iet-gtd:20060296
- Type: Article
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p.
484
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Here, a comprehensive characterisation of the performance of voltage relays, focusing on their capability to detect islanding of embedded synchronous generators is presented. Such characterisation is done by using the performance curves and the concept of critical reactive power imbalance, which allows a systematic analysis of voltage relays considering a wide range of system operating points. The impacts of important factors on the relay performance are evaluated, such as the presence of voltage-dependent loads and the generator exciter control mode. Moreover, a graphical approach that allows protection engineers to adjust voltage relays to reach two objectives simultaneously: (i) to be sensitive enough to detect islanding efficiently and (ii) to satisfy the protection requirements against abnormal voltage variation is proposed. Results can be quite attractive to understand voltage relays behaviour and limitations and thus, they can be adjusted more efficiently. - Author(s): Q. Zhou and J.W. Bialek
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 492 –498
- DOI: 10.1049/iet-gtd:20060246
- Type: Article
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p.
492
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The issue of congestion management in distribution networks by considering a methodology for generation curtailment due to voltage constraints is addressed. The curtailment is based on the contribution of generators to the constraints as quantified by voltage-sensitivity factors. It has been shown that generation curtailment following a simple proportionality rule is not efficient and some alternatives, which give a more efficient outcome, have been proposed. Influence of network losses on the curtailment rules has also been shown. The considerations have been illustrated using two simple 11 kV networks. - Author(s): A.C. Zambroni de Souza ; C.B. Rosa Júnior ; B. Isaias Lima Lopes ; R.C. Leme ; O.A.S. Carpinteiro
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 499 –505
- DOI: 10.1049/iet-gtd:20060310
- Type: Article
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Here the use of a non-iterative (NI) method for load-flow solutions is investigated. The method, previously proposed in the literature, presents some advantages in comparison with the iterative approaches usually employed. There, because the Taylor expansion is used, the power flow Jacobian matrix is not updated along the process. Here, some improvements in the implementation are executed, and few control actions are incorporated into the formulation. The method is then applied for voltage stability studies, aiming to reduce the computational time associated with. - Author(s): E.E. Ahmed and W. Xu
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 506 –515
- DOI: 10.1049/iet-gtd:20060316
- Type: Article
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p.
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An iterative frequency domain-based harmonic analysis method for harmonic distortion assessment for systems with distributed harmonic sources has been proposed. The proposed method, unlike the traditional method, is able to consider harmonic attenuation and diversity due to the interaction between the harmonic sources and power grid. Time domain simulation for systems with distributed adjustable speed drives is used to validate the proposed method. Case studies are conducted to show the merits of the proposed method especially with a large number of distributed harmonic sources. - Author(s): F. Milano ; A.J. Conejo ; R. Zárate-Miñano
- Source: IET Generation, Transmission & Distribution, Volume 1, Issue 3, p. 516 –526
- DOI: 10.1049/iet-gtd:20060407
- Type: Article
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p.
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General sensitivity formulas for maximum loading conditions of nonlinear power systems have been proposed. The proposed formulas allow computing the sensitivities of any system variable and, in particular, of the maximum loading margin with respect to arbitrary parameters. This approach extends previous results. It has also been shown that the sensitivity formulae available in the literature for static saddle-node and limit-induced bifurcation points are particular cases of the proposed general formulae. Two benchmark systems, namely a 6-bus system and the IEEE RTS-96 24-bus tests system, are used to illustrate and test the proposed technique.
Small-signal dynamic model of a micro-grid including conventional and electronically interfaced distributed resources
Load behaviour prediction under blackout conditions using a fuzzy expert system
Risk management of generators' strategic bidding in dynamic oligopolistic electricity market using optimal control
Application of the multi-level current reinjection concept to HVDC transmission
Probability-based predictive self-healing reconfiguration for shipboard power systems
Dynamic optimal power flow approach to account for consumer response in short term hydrothermal coordination studies
Representative static load models for transient stability analysis: development and examination
Harmonic and reactive power compensation as ancillary services in inverter-based distributed generation
Operating reserve capacity requirements and pricing in deregulated markets using probabilistic techniques
Simulated annealing-based optimal wind‐thermal coordination scheduling
Unit commitment computation by fuzzy adaptive particle swarm optimisation
Fast prediction of loadability margins using neural networks to approximate security boundaries of power systems
Transient stability constrained optimal power flow using particle swarm optimisation
Characteristics of voltage relays for embedded synchronous generators protection
Generation curtailment to manage voltage constraints in distribution networks
Non-iterative load-flow method as a tool for voltage stability studies
Assessment of harmonic distortion level considering the interaction between distributed three-phase harmonic sources and power grid
General sensitivity formulas for maximum loading conditions in power systems
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